Q&A - P3 Math

[HAPPYH]

peapot:

Hi what method to use for this q?


Darren has some 10cent coins, 20cent coins and 50 cent coins in his pocket that add up to $2. He has exactly 9 coins. How many 20 cent coins does he have?

I found 2 answers. either 3 twenty cent coins or 7 twenty cent coin. Which should be correct?

Other than guess and check, is there any other way to solve this problem (3 variables)? For example, there are few steps we can follow if there is 2 variables (cows and ducks or cars and bicycles) to arrive at the answer. Similarly, is there anything that we can follow to do this sum? My DD can do guess and check only if it is small numbers. Worried what if the numbers get bigger and bigger. Thank you in advance.

[Divha]

Hi,


Could anybody help to solve this problem using model ?

Gina had $75 and Wendy had $125.
After Wendy gave Gina some money, she had $40 less than Gina. How much money did Wendy give to Gina ?

Thanks a lot.

[VbusyMum]

Divha:

Hi,


Could anybody help to solve this problem using model ?

Gina had $75 and Wendy had $125.
After Wendy gave Gina some money, she had $40 less than Gina. How much money did Wendy give to Gina ?

Thanks a lot.

The answer is $5. I don't know how to draw model using my iPad. Attempted below. Hope it is clear. \"X\" is the part that is transfer so u need to find the remaining 2 units (marked as ?) after putting aside the 40 which is extras from the original 50. The difference divide by the 2 units.

Do ignore the EXT as I have to out it there to make sure the 50 is mark in the correct position of the model.

Workings:
50-40=10
10/2=5

Ext |_____________|<----50------->

W. |_____75______|_?_|_40_|_X_|

G. |_____75______|_?_|

[php]

Divha:

Hi,


Could anybody help to solve this problem using model ?

Gina had $75 and Wendy had $125.
After Wendy gave Gina some money, she had $40 less than Gina. How much money did Wendy give to Gina ?

Thanks a lot.

Using Total Unchanged Concept to solve the problem

After Model :-

Wendy <---------------->
1 unit
Gina <-------------------------------->
1 unit + $40

2 units + $40 --> $200
2 units --> $160
1 unit --> $80

Before : Wendy --> $125
After : Wendy -- > $80

Ans : $125 - $80 = $45....

[Lynn2010]

Ans is 45

[Divha]

Thanks a lot PHP for your detailed solution. Easy to explain to my DS. Thanks.

[fohope]

Hi,

Pls help me to solve these problems and thanks in advance to everyone.

1) 21 handshakes were exchanged at a party. If each person only shook hand with another person once, how many people were there at the party?

2) Alex and Eugene have an equal number of marbles at first.
After Alex give Eugene 20 marbles, Eugene has twice as many marbles as Alex.
How many marbles does Alex have at first?

for question 2, can draw the model for me.

[php]

fohope:

Hi,

Pls help me to solve these problems and thanks in advance to everyone.

2) Alex and Eugene have an equal number of marbles at first.
After Alex give Eugene 20 marbles, Eugene has twice as many marbles as Alex.
How many marbles does Alex have at first?

Using Total Unchanged Concept,

Before
Alex - 1u, Eugene - 1u, Total - 2u

After
Alex - 1p, Eugene - 2p, Total - 3p

Make the total units similiar,

Before
Alex - 3p, Eugene - 3p, Total - 6p

After
Alex - 2p, Eugene - 4p, Total - 6p

1 unit = 20
3 units = 20 x 3 = 60

Ans : 60

[tianzhu]

fohope:

for question 2, can draw the model for me.

Hi

Hope this helps.

Best wishes

http://farm8.staticflickr.com/7089/7201776920_8228f273ec_z.jpg\">

[tianzhu]

fohope:

Hi,

Pls help me to solve these problems and thanks in advance to everyone.
1) 21 handshakes were exchanged at a party. If each person only shook hand with another person once, how many people were there at the party?

Hi

This question is pretty similar to yours.Try to understand the logic behind the solution and apply it to your question.

The answer to your question is 7.

Best wishes.

http://farm6.staticflickr.com/5307/5668798707_dd4d6f1925_z.jpg\">